(1) Field of the Invention
This invention relates to a thermoplastic resin composition containing a titanium dioxide pigment, and a process for preparing the thermoplastic resin composition.
The titanium dioxide pigment-containing thermoplastic resin composition is suitable as a raw material for a highly white film and especially a coating material-for photographic resin-coated paper, and a master batch for the preparation of a thermoplastic resin composition used as a coating material for coated paper.
(2) Description of the Related Art
To improve dispersibility of a titanium dioxide pigment in a resin, a technique for coating a titanium dioxide pigment particle with an inorganic surface treating agent is generally employed. Namely, about 0.1 to 2% by weight of an inorganic surface treating agent is used as a coating material which includes aluminum oxide hydrate, silicon oxide hydrate, titanium oxide hydrate, zirconium oxide hydrate, zinc hydroxide, magnesium hydroxide, manganese compounds and phosphoric acid compounds. Of these, aluminum oxide hydrate and silicon oxide hydrate are preferably used.
As means for coating one surface or both surfaces of a substrate such as paper or a polyester film with a thermo-plastic resin composition containing a titanium dioxide pigment, an extrusion lamination process is generally employed.
In recent years, a high degree of whiteness and a high degree of opacity are required for coated paper and film, and therefore a thermoplastic resin composition containing a titanium dioxide pigment at a high concentration is used. However, the dispersion of titanium dioxide pigment in the conventional thermoplastic resin composition is poor, and thus, the state of a titanium dioxide coating is poor. Namely, the coated paper and film have a poor surface smoothness or bubbles within the coating.